(CNN) --The recent disappearance of a Boeing 727 along with a resurgence of terror activities near the Horn of Africa have spurred the United States to add new combat power to the region, the senior U.S. commander based in the area has said.

"We've been in a more aggressive posture for over a month," Marine Brig. Gen. Mastin Robeson, commander of the Combined Joint Task Force Horn of Africa, told The Associated Press in a telephone interview from Djibouti on Friday.

The Horn of Africa sits across the Gulf of Aden from Yemen, which is the homeland of al Qaeda leader Osama bin Laden.

Robeson told CNN he had identified an "operational need" for Air Force F-16 and F-15E aircraft along with Navy F/A-18s, when a Boeing 727 vanished after leaving Angola's Luanda airport in May.

He has asked the Pentagon to reassign the aircraft to the French military base in Djibouti. It is unclear when the Pentagon might act on his request.

U.S. officials are not sure what happened to the 727, but they say the possibility exists that the aircraft is in the hands of terrorists. Other reports have suggested the plane's owner took it from the airport in a financial dispute.

"We have the ability to identify it from other airplanes in the air," Robeson said. He added that if it appears, the U.S. military "would not hesitate to shoot it down."

Robeson noted that all 727s in the region fly on approved commercial air routes, so if this plane were to appear suddenly, it would be deemed a threat. He noted the continuing threat of an attack from aircraft in the region.

The Horn of Africa sits across from Yemen, Osama bin Laden's homeland.

Robeson said the U.S. fighter aircraft are being requested in order to pursue a "more aggressive campaign" against terrorists in the region now that the situation in Iraq no longer requires large numbers of aircraft to conduct missions.

There have been intermittent deployments of fighters to the Horn of Africa in the past, but mainly on long missions that originate and then return to bases in the Persian Gulf.

By deploying from Djibouti, the planes could fly over the area for longer periods of time than planes that must refuel elsewhere.

Robeson said his request is for four to six aircraft to be deployed from Camp Lemonier on an intermittent basis. They would supplement French Mirage jets and radars providing air-defense coverage for the base.

But, he said, the planes could potentially be used to protect U.S. ground forces involved in any future military counterterrorism missions.

The request to put planes in Djibouti "signals an increased emphasis on the counterterrorism war in the Horn of Africa," Robeson said. According to the AP, Robeson referred directly to al Qaeda as a target of "selective actions."

Robeson told the AP that in the past four months, he's noticed "a pretty active flow" of terrorists into or through the Horn of Africa.

Marine Brig. Gen. Mastin Robeson on the missing 727: The U.S. military "would not hesitate to shoot it down."

"We've definitely seen an increase not just in presence but in active transnational terrorist planning" he told the AP.

This week, a U.S. military assessment team has been at Camp Lemonier to try to determine what it would take to have the Air Force and Navy aircraft operate out of the base on a routine, temporary basis, according to a statement released by the Pentagon on Thursday.

The Combined Joint Task Force for the Horn of Africa, formed in late 2002, is charged with conducting any operations that might be needed to counter terrorist activities in the region, including in Yemen.

Between 1,300 and 1,600 U.S. ground forces are stationed at Camp Lemonier, according to the AP. They include infantry and special operations forces from all the services. Helicopters and refueling aircraft are based there, but no fighters or bombers, the AP reported.